In conventional distributed computing systems, received messages are added to a queue, and are automatically executed once they reach the head of the queue. Clients and services may include sets of rules that determine how to interpret the messages, how to process the messages, and so on. For example, when a service receives messages from a first client, it may apply rule A to perform a first action, and when the service receives messages from a second client, it may apply rule B to perform a second action. If a received message is in a format that cannot be interpreted by the recipient, then it is not processed. However, such conventional distributed computing systems do not include a mechanism for establishing a contractual arrangement associated with the messages before those messages are processed.